A marketing executive wishes to estimate the average monthly sales of a particular brand of gold necklace in local shops. He decides that an estimate, correct with 3% of the population average with a probability of 0.9545(2 standard errors) shall be considered dependable. How big a sample of shops is needed? Assume that based on a previous enquiry, the coefficient of variation of monthly sales of that particular brand of gold necklace is 9%. Here C.V.is 0.09 so So the sample size should be 6 times the monthly average sales of that particular brand of gold necklace.